Image pickup apparatus, lens unit, and methods of controlling the same

ABSTRACT

An image pickup apparatus detachably mounting a lens unit including a plurality of optical members includes an image pickup unit that accumulates charge in synchronization with a vertical synchronizing signal to generate an image signal, and a control unit that generates control information for each of the plurality of optical members of the mounted lens unit and communicates the control information with the lens unit in synchronization with the vertical synchronizing signal. The control unit is configured to perform a first communication in synchronization with the vertical synchronizing signal, and to perform a second communication, for controlling an optical member different to the optical before a next first communication that is performed in synchronization with a next vertical synchronizing signal. The first communication and the second communication are predetermined packet communications in which optical members to be controlled among the plurality of optical members are different from each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens unit, and an image pickupapparatus capable of mounting the lens unit.

2. Description of the Related Art

Recently, in methods of automatic focusing a camera, the most commonmethod is of obtaining a TVAF evaluation value that represents thesharpness of an image from an image signal obtained by a photoelectricalconversion of an object. Focusing is performed by controlling a focuslens position so that the television auto-focus (TVAF) evaluation valuepeaks (hereinafter, TVAF method).

Generally, the TVAF evaluation value in the TVAF method is generatedusing a level of a high-frequency content of an image signal extractedby a band-pass filter. This is because, when a normal object ispicked-up, the TVAF evaluation value increases as a focus lens comesclose to an in-focus position. This is illustrated in FIG. 2, and thepoint where the level of the TVAF evaluation value peaks is the in-focusposition for the object.

As a lens control of the TVAF method, there is an operation of detectingan in-focus direction based on a change of a TVAF evaluation value whena focus lens is minutely moved to back and forth between aclose/infinity side as illustrated in FIG. 3 (hereinafter, reciprocatingoperation). Since the TVAF evaluation value is generated based on theimage signal, it is necessary that the reciprocating operation issynchronized with a vertical synchronizing signal of an image pickupelement.

Japanese patent Laid-Open No. H11-125860 describes that aninterchangeable lens camera system in which a camera unit generates aTVAF evaluation value and transfers the TVAF evaluation value to a lensunit in communication, and in which the lens unit performs a TVAFcontrol.

On the other hand, in case that the TVAF control is performed not in alens unit as Japanese patent Laid-Open No. H11-125860 but in a cameraunit, a driving instruction of the focus lens is generated based on theTVAF evaluation value in the camera unit, and the driving instruction istransmitted to the lens unit. In this case, when a single communicationis performed in synchronization with the vertical synchronizing signalas Japanese patent Laid-Open No. H11-125860, it becomes like FIG. 4. InFIG. 4, in a single communication during one vertical synchronizing timeperiod as before, information on a lens position is transmitted from thelens unit to the camera unit, and the driving instruction of the focuslens is transmitted from the camera unit to the lens unit. Accordingly,the camera unit performs an AF control based on focus lens positioninformation obtained from the lens unit within the verticalsynchronizing time period, and transmits the focus lens drivinginstruction in communication within the next vertical synchronizing timeperiod. Therefore, it causes a problem because the focus lens drivinginstruction cannot be immediately transmitted based on the lens positioninformation obtained from the lens unit thereby introducing a controlcycle delay (responsiveness delay of AF). Further, in case of performinga control of a stop included in the lens unit on the basis of aninstruction from the camera unit, the responsiveness of the auto-focus(AF) may deteriorate due to a load of an auto-exposure (AE) control forgenerating a stop control instruction.

SUMMARY OF THE INVENTION

The present invention provides an image pickup apparatus and a lens unitthat enables an AF operation having a good responsiveness even when aTVAF control is performed on an image pickup apparatus side.

An image pickup apparatus as one aspect of the present inventiondetachably mounts a lens unit including a plurality of optical members,and includes an image pickup unit configured to accumulate charge insynchronization with a vertical synchronizing signal to generate animage signal, and a control unit configured to generate controlinformation for each of the plurality of optical members of the mountedlens unit and configured to communicate the control information with thelens unit in synchronization with the vertical synchronizing signal. Thecontrol unit is configured to perform a first communication insynchronization with the vertical synchronizing signal, and to perform asecond communication, for controlling an optical member different to theoptical before a next first communication that is performed insynchronization with a next vertical synchronizing signal. The firstcommunication and the second communication are predetermined packetcommunications in which optical members to be controlled among theplurality of optical members are different from each other.

A lens unit as another aspect of the present invention is detachablymounted on an image pickup apparatus including an image pickup unit thataccumulates a charge in synchronization with a vertical synchronizingsignal to generate an image pickup signal, and includes a plurality ofoptical members, and a lens control unit configured to communicate withan image pickup apparatus to which the lens unit is mounted and tocontrol a drive of the plurality of optical members on the basis ofinformation received from the image pickup apparatus. The lens controlunit is capable of communicating with the image pickup apparatus insynchronization with a vertical synchronizing signal received from theimage pickup apparatus. The lens control unit performs a firstcommunication in synchronization with the vertical synchronizing signal,and then performs a second communication before a next firstcommunication that is performed in synchronization with a next verticalsynchronizing signal. The first communication and the secondcommunication are predetermined packet communications in which opticalmembers to be controlled among the plurality of optical members aredifferent from each other.

A lens unit as another aspect of the present invention is detachablymounted on an image pickup apparatus including an image pickup unit thataccumulates a charge in synchronization with a vertical synchronizingsignal to generate an image signal, and includes a plurality of opticalmembers including a focus lens, and a lens control unit configured tocommunicate with an image pickup apparatus to which the lens unit ismounted and to control a drive of the plurality of optical members onthe basis of information received from the image pickup apparatus. Thelens control unit is capable of communicating with the image pickupapparatus in synchronization with a vertical synchronizing signalreceived from the image pickup apparatus. The lens control unit performsa first communication in synchronization with the vertical synchronizingsignal, and then performs a second communication before a next firstcommunication that is performed in synchronization with a next verticalsynchronizing signal. The lens control unit controls a drive of thefocus lens on the basis of information received in the secondcommunication, and controls a drive an optical member other than thefocus lens on the basis of information received in the firstcommunication.

A lens unit as another aspect of the present invention is detachablymounted on an image pickup apparatus including an image pickup unit thataccumulates charge in synchronization with a vertical synchronizingsignal to generate an image pickup signal, and includes a plurality ofoptical members including a stop and a focus lens, and a lens controlunit configured to communicate with an image pickup apparatus to whichthe lens unit is mounted and to control a drive of the plurality ofoptical members on the basis of information received from the imagepickup apparatus. The lens control unit is capable of communicating withthe image pickup apparatus in synchronization with a verticalsynchronizing signal received from the image pickup apparatus. The lenscontrol unit performs a first communication in synchronization with thevertical synchronizing signal, and then performs a second communicationbefore a next first communication that is performed in synchronizationwith a next vertical synchronizing signal. The lens control unitcontrols a drive of the focus lens on the basis of information receivedin the second communication, and controls a drive of the stop on thebasis of information received in the next first communication.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for explaining a configuration of a lens unit and acamera unit in embodiment of the present invention.

FIG. 2 is a diagram for explaining a relationship between a TVAFevaluation value and a focus lens position.

FIG. 3 is a diagram for explaining reciprocating operation of a TVAFcontrol.

FIG. 4 is a diagram for explaining a control delay in a traditionalcommunication between the lens unit and the camera unit.

FIG. 5 is a flowchart of a camera processing in embodiment of thepresent invention.

FIG. 6 is a flowchart of the TVAF control in embodiment of the presentinvention.

FIG. 7 is a flowchart of reciprocating operation in embodiment of thepresent invention.

FIG. 8 is a diagram for explaining the reciprocating operation inembodiment of the present invention.

FIG. 9 is a diagram for explaining a timing of an accumulation of a CMOSsensor in embodiment of the present invention.

FIG. 10 is a timing chart of processing of a camera microcomputer and alens microcomputer in embodiment of the present invention.

FIG. 11 is a diagram for explaining a serial communication in embodimentof the present invention.

FIG. 12 illustrates content of communication data in embodiment of thepresent invention.

FIG. 13 is a diagram for explaining a usual command communication.

FIG. 14 is a flowchart of a peak-climbing drive in embodiment of thepresent invention.

FIG. 15 is a diagram for explaining the mountain-climbing drive in anembodiment of the present invention.

FIG. 16 is a diagram for explaining a malfunction caused in acommunication between the lens unit and the camera unit.

FIG. 17 is a diagram for explaining prevention against the malfunctioncaused in an embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiments of the present invention will hereinafter bedescribed with reference to the accompanying drawings. FIG. 1illustrates a configuration of a camera system in an embodiment of thepresent invention.

In FIG. 1, a lens unit 117 (hereinafter also referred to as “lens”) thatis an accessory is configured to be capable of being put on and takenoff from a camera unit 118 (hereinafter also referred to “camera” or“image pickup apparatus”) via a mount (not illustrated). The camera unit118 can be mounted with the lens unit 117. The lens unit 117 and cameraunit 118 forms a so-called interchangeable lens system.

In FIG. 1, the lens unit 117 includes an image pickup optical system 101to 105 thereinside. In this embodiment, a first lens unit 101 and athird lens unit 104 are fixed. A second lens unit 102 is a lens unit forvarying a magnification (hereinafter referred to as“magnification-varying lens”). An stop 103 adjusts the amount ofincident light to an image pickup element 106. A fourth lens unit 105 isa lens unit that has both a focusing function and a compensationfunction of correcting a movement of a focus plane due tomagnification-varying (hereinafter referred to as “focus lens”). Theabove-mentioned configuration of the image pickup optical system in thelens unit 117 is an example, and the invention is not limited to theconfiguration. Light from an object passes through the image pickupoptical system 101 to 105 and forms an image on the image pickup element106 consisting of a CMOS sensor and the like in the camera unit 118.

The image pickup element 106 in the camera unit 118 is a photoelectricalconversion element that is formed by a CMOS sensor or the like. Theimage pickup element 106 generates an image signal by a photoelectricalconversion of an object image, and the image signal is input to a camerasignal processing circuit 108 after the image signal is amplified to anoptimal level by an amplifier 107.

The camera signal processing circuit 108 provides various types of imageprocessings for output signals from the amplifier 107, and generates animage. Further, the camera signal processing circuit 108 generates avalue of an integral of a brightness signal of the image signal as AEevaluation value. The AE evaluation value is output to a cameramicrocomputer 116. A monitor display 109 is formed by a LCD or the like,and displays the image from the camera signal processing circuit 108. Arecording unit 110 records the image from the camera signal processingcircuit 108 to a storage medium, such as a semiconductor memory.

A TVAF gate 113 permits the passage of only signals of areas used forfocus detection among output signals from the amplifier 107 in allpixels. The TVAF signal processing circuit 114 generates a TVAFevaluation value by extracting high-frequency components from a signalthat has passed through the TVAF gate 113. The TVAF evaluation value isoutput to the camera microcomputer 116. The TVAF evaluation valuerepresents the sharpness (contrast state) of a picked-up image generatedbased on an image signal from the image pickup element 106, and as aresult, is used as a signal representing a focus state of the imagepickup optical system as illustrated in FIG. 2 because the sharpnessvaries according to the focus state of the image pickup optical system.

The camera microcomputer 116 as a controller controls an operation in awhole camera, and controls the TVAF gate 113 so as to set a TVAF frameat a predetermined rate to the image. The camera microcomputer 116performs a TVAF control based on the TVAF evaluation value obtained fromthe TVAF signal processing circuit 114, and transmits a desired drivinginstruction of the focus lens to the lens microcomputer 115. Further,the camera microcomputer 116 performs an AE control based on the AEevaluation value obtained from the camera signal processing circuit 108,and transmits a desired driving instruction of the stop to the lensmicrocomputer 115. As above, the camera microcomputer 116 and the lensmicrocomputer 115 are formed so as to be capable of communicating witheach other.

A zoom driving source 111 in the lens unit 117 is a driving source fordriving the magnification-varying lens 102. A focus driving source 112is a driving source for driving the focus lens 105, which is a firstoptical member. The zoom driving source 111 and the focus driving source112 are formed by an actuator, such as a stepping motor, a DC motor, avibration motor, and a voice coil motor. Further, a stop driving source119 in the lens unit 117 is a driving source for driving the stop 103 asa second optical member.

The lens microcomputer 115, which is the lens controller, receives adriving instruction of the focus lens 105 from the camera microcomputer116, and performs focusing by driving the focus lens 105 in an opticalaxis direction by the focus driving source 112 on the basis of thedriving instruction. The lens microcomputer 115 receives a drivinginstruction for the stop 103 from the camera microcomputer 116, andadjusts the amount of light passing through the image pickup opticalsystem by driving the stop 103 with the focus driving source 119.Further, the lens microcomputer 115 receives a driving instruction ofthe magnification-varying lens 102 from the camera microcomputer 116,and performs zooming by driving the magnification-varying lens 102 in anoptical axis direction by the zoom driving source 111 on the basis ofthe driving instruction.

Moreover, a communication of data is performed between the cameramicrocomputer 116 and the lens microcomputer 115. The image pickupelement 106 performs a charge accumulation within a predeterminedduration in a vertical synchronizing time period that is a cycle of avertical synchronizing signal output from a signal generating circuit120. The camera microcomputer 116 transmits the vertical synchronizingsignal to the lens microcomputer 115, and as described below, the cameramicrocomputer 116 and the lens microcomputer 115 communicate based on atiming of the vertical synchronizing signal.

Next, a processing performed in the camera microcomputer 116 in thecamera unit 118 will be described with reference to FIG. 5. Theprocessing is executed according to a computer program that is stored inthe camera microcomputer 116. After-mentioned Steps 502 to 511 areperformed during one vertical synchronizing time period.

Step 501 indicates a start of the processing. In Step 502, the cameramicrocomputer 116 waits the output of the vertical synchronizing signalto time the communication.

In Step 503, the camera microcomputer 116 communicates with the lensmicrocomputer 115 (first communication), and acquires a position of thefocus lens.

In Step 504, the camera microcomputer 116 clears an effective bit(details describe below) of a driving instruction in a communicationbuffer. In this embodiment, the effective bit of the driving instructionis cleared after the first communication of Step 503, but the inventionis not limited to the configuration and may be configured to clear theeffective bit within a time period from after a second communication inStep 511 to before the next first communication in Step 503. Inparticular, it is only necessary that the effective bit is cleared fromafter the second communication in Step 511 to before TVAF processing inStep 506 in the next vertical synchronizing time period.

In Step 505, various task processings of Step 506 to 509 including aTVAF processing that is performed in the camera microcomputer 116 insynchronization with the vertical synchronizing signal are invoked. InStep 506, the camera microcomputer 116 performs the TVAF processing, andin Step 507 to 509, the camera microcomputer 116 performs the othercamera processings.

In Step 510, the camera microcomputer 116 monitors whether the TVAFprocessing has completed and whether a predetermined time period haselapsed from the output of the vertical synchronizing signal. When theTVAF processing has completed or the predetermined time period haselapsed from the output of the vertical synchronizing signal, itproceeds to Step 511, and the camera microcomputer 116 communicates withthe lens microcomputer 115 (second communication) and transmits thedriving instruction of the focus lens. Even if the TVAF processing hasnot been completed, when the predetermined time period has elapsed fromthe output of the vertical synchronizing signal, it proceeds to Step511. Then, it returns to Step 502, and the next vertical synchronizingsignal is timed.

Next, a TVAF control that is performed in the camera microcomputer 116in the camera unit 118 will be described with respect to the drawingsfrom FIG. 6. The TVAF control is executed according to the computerprogram stored in the camera microcomputer 116.

Step 601 indicates a start of the processing. In Step 602, the cameramicrocomputer 116 acquires a TVAF evaluation value. In Step 603, thecamera microcomputer 116 determines whether the mode of the TVAFprocessing is set to a reciprocating mode. The reciprocating modedenotes a mode that determines whether an in-focus state has beenreached and, when the in-focus state has not been reached, determines afocus drive direction towards an in-focus position. The details of theoperations of the reciprocating mode are described with reference toFIG. 7. If the TVAF processing mode is set to the reciprocating mode, itproceeds to Step 604 and the reciprocating operation is performed, andif the TVAF processing mode is not set to the reciprocating mode, itproceeds to Step 613.

In Step 604, the camera microcomputer 116 performs the reciprocatingoperation, and in Step 605, the camera microcomputer 116 determineswhether the in-focus state has been detected in Step 604. If thein-focus state has been detected, it proceeds to Step 609, and thecamera microcomputer 116 performs a setting for driving the focus lensto the in-focus position. Then, the camera microcomputer 116 changes themode to a stop mode in Step 610, sets the effective bit of the drivinginstruction in Step 611, and ends the processing in Step 612. If it isdetermined in Step 605 that the in-focus state has not been detected, itproceeds to Step 606.

In Step 606, the camera microcomputer 116 determines whether thedirection of the in-focus position has been determined. If the directionhas been determined, it proceeds to Step 607, and the cameramicrocomputer 116 performs a setting for performing a peak-climbingdrive toward the determined direction. The camera microcomputer 116changes the mode to a peak-climbing mode in Step 608, sets the effectivebit of the driving instruction in Step 611, and ends the processing inStep 612. If the direction of the in-focus position has not beendetermined, it proceeds to Step 611, and the camera microcomputer 116sets the effective bit of the driving instruction, and the processing isended in Step 612.

In Step 613, the camera microcomputer 116 determines whether the mode ofthe TVAF processing is set to the stop mode. The stop mode denotes amode for moving the focus lens to the in-focus position and stopping it.If the mode is set to the stop mode, it proceeds to Step 614, and thecamera microcomputer 116 determines whether the focus lens has moved tothe in-focus position in TVAF. If the mode is not set to the stop mode,it proceeds to Step 617.

If the focus lens has moved to the in-focus position of the TVAF in Step614, it proceeds to Step 615. If the focus lens has not moved to thein-focus position in the TVAF, it proceeds to Step 611 and the cameramicrocomputer 116 sets the effective bit of the driving instruction, andthe processing is ended in Step 612. In Step 615, the cameramicrocomputer 116 holds a TVAF evaluation value of the in-focusposition, and in Step 616, the camera microcomputer 116 changes the modeto a reboot mode. Then, it proceeds to Step 611 and the cameramicrocomputer 116 sets the effective bit of the driving instruction, andthe processing is ended in Step 612.

In Step 617, it is determined whether the mode of the TVAF processing isset to the reboot mode. When a change occurs during monitoring of theTVAF evaluation value after the focusing is stopped, the reboot modedenotes a processing to active the TVAF again on the assumption that anobject to be taken is changed. If the mode is set to the reboot mode, itproceeds to Step 618 and the camera microcomputer 116 determines whetherthe TVAF evaluation value is changed a lot. If the mode is not set tothe reboot mode, it proceeds to Step 620.

If the TVAF evaluation value is changed a lot (e.g. by an amount greaterthan a predetermined threshold) in Step 618, it proceeds to Step 619. Ifnot, it proceeds to Step 611 and the effective bit of the drivinginstruction is set, and the processing is ended in Step 612. The cameramicrocomputer 116 changes the mode of the TVAF processing to thereciprocating mode in Step 619, it proceeds to Step 611 and the cameramicrocomputer 116 sets the effective bit of the driving instruction, andthe processing is ended in Step 612.

In Step 620, the camera microcomputer 116 performs the peak-climbingdrive for the focus lens 105 in the direction determined in Step 604 ata predetermined speed, a position of the focus lens at which the TVAFevaluation value peaks is sought based on a relationship of the TVAFevaluation value and the focus lens position acquired from the lensmicrocomputer 115. The detailed operations of the peak-climbing drivewill be described with reference to FIG. 14.

In Step 621, the camera microcomputer 116 determines whether a focuslens position at which the TVAF evaluation value peaks is detectedduring the peak-climbing drive operation. If the peak focus lensposition is detected, it proceeds to Step 622, and if not, it proceedsto Step 611 and the camera microcomputer 116 sets the effective bit ofthe driving instruction, and the processing is ended in Step 612.

In Step 622, the camera microcomputer 116 performs the setting so as toreturn the focus lens to the focus lens position at which the TVAFevaluation value peaks during the peak-climbing drive operation. In Step623, the camera microcomputer 116 determines whether the focus lens isreturned to the focus lens position at which the TVAF evaluation valuepeaks. If the focus lens is returned to the focus lens position of thepeak, the camera microcomputer 116 sets the mode of the TVAF processingto the reciprocating mode in Step 624. If the focus lens is not returnedto the peak focus lens position, it proceeds to Step 611 and the cameramicrocomputer 116 sets the effective bit of the driving instruction, andthe processing is ended in Step 612.

As above, if the TVAF processing has been completed, the effective bitof the driving instruction is set, and if the TVAF processing has notbeen completed, the effective bit of the driving instruction is kept ata state that is cleared in Step 504 of FIG. 5.

The reciprocating operation will be described with reference to FIG. 7.

Step 701 indicates a start of the processing.

In Step 702, the camera microcomputer 116 waits the output of thevertical synchronizing signal to time the communication.

In Step 703, the camera microcomputer 116 communicates informationincluding the focus lens position with the lens microcomputer 115. Thiscommunication is a fixed-length packet communication.

In Step 704, the camera microcomputer 116 calculates a drive cycle and adrive delay time period. The drive cycle denotes a time period from astart of a drive of the focus lens to the close (infinity) side to astart of a next drive to the infinity (close) side. The drive delay timeperiod denotes a time period from the output of the verticalsynchronizing signal to the start of the drive of the focus lens.Alternatively, the drive delay time may be defined on a basis of acharge accumulation start timing of the image pickup element 106 forproducing the image signal or on a basis of a delay time from (that is,on a basis of) the start of after-mentioned first communication. Thedrive cycle is set to 2V and the drive delay time period is set to ½V inthis embodiment, but those are not limited to the values.

In Step 705, the camera microcomputer 116 determines whether the currentmode is 0. If it is 0, it proceeds to Step 706 and the cameramicrocomputer 116 performs after-mentioned processing at the focus lensposition on the close side, and if it is not 0, it proceeds to Step 711.

<Processing at Focus Lens Position on Close Side>

In Step 706, the camera microcomputer 116 stores the TVAF evaluationvalue as a TVAF evaluation value on an infinity side, which is based onthe output of the sensor that is accumulated when the focus lens islocated on the infinity side.

An adding is performed for “Mode” (when it is 4 or more, it is returnedto 0) in Step 707, and it proceeds to Step 708.

<Common Processing>

If a direction is determined as the in-focus direction for a firstpredetermined number of times in a row at Step 708, it proceeds to Step727, and if not, it proceeds to Step 709.

In Step 709, if the focus lens repeatedly gets there and back in thesame area for a second predetermined number of times in a row, itproceeds to Step 728, and if the focus lens does not repeatedly getthere and back in the same area for a second predetermined number oftimes in a row, it proceeds to Step 710.

In Step 710, the camera microcomputer 116 communicates informationincluding the driving instruction with the lens microcomputer 115, andit returned to Step 702. This communication is a fixed-length packetcommunication.

In Step 727, the camera microcomputer 116 recognizes that the directionhas been determined, and it proceeds to Step 730 and the processing isended to transmit the peak-climbing drive.

In Step 728, the camera microcomputer 116 calculates an average positionof the focus lens position during the predetermined time period as anin-focus position. In Step 729, the camera microcomputer 116 recognizesthat the in-focus state has been determined, and it proceeds to Step 730and the processing is ended to transit the stop of the focusing or thedetermination of the reboot.

In Step 711, the camera microcomputer 116 determines whether the current“Mode” is 1. If it is 1, it proceeds to Step 712 and a processing ofdriving after-mentioned focus lens 105 in the infinity direction, and ifnot, it proceeds to Step 718.

<Processing to Drive Focus Lens to Infinite Side>

In Step 712, the camera microcomputer 116 calculates reciprocationamplitude and center movement amplitude in the reciprocating. Althoughthe details are not described here, in general, with reference to thedepth of focus, the amplitude is made smaller when the depth is shallowand is made larger when the depth is deep. The reciprocation amplitudedenotes a movement amount of the focus lens from the close side to theinfinity side in when there is not a movement of the center position ofthe reciprocation (center movement). The center movement amplitudedenotes a movement amount of the center position of the reciprocation.The camera microcomputer 116 calculates the reciprocation amplitude andthe center movement amplitude as a value of a movement amount of animage plain. This is because the proportion (sharpness) of the imageplane movement amount to the drive amount of the focus lens differs witheach lens unit and it is necessary to acquire detailed information onthe specification of the lens unit at every mounting of a new lens unitin order that the camera calculates a real drive amount of the focuslens.

In Step 713, the camera microcomputer 116 compares the above-mentionedTVAF evaluation value of the infinity side in Mode=0 withafter-mentioned TVAF evaluation value of the close side in Mode=2. Ifthe infinity side TVAF evaluation value is larger than the close sideTVAF evaluation value, it proceeds to Step 714, and if the infinity sideTVAF evaluation value is not larger than the close side TVAF evaluationvalue, it proceeds to Step 715.

In Step 714, the driving amplitude is defined using the followingexpression:driving amplitude=reciprocation amplitude+center movement amplitude

In Step 715, the driving amplitude is defined using the followingexpression:driving amplitude=reciprocation amplitude

In Step 716, the camera microcomputer 116 determines that the focus lensis driven in the infinity direction on the driving amplitude defined inStep 714 or Step 715.

An adding is performed for “Mode” (when it is 4 or more, it is returnedto 0) in Step 717, and it proceeds to Step 708. The processings in Step708 and below are as described above.

In Step 718, it is determined whether the current “Mode” is 2. If it is2, it proceeds to Step 719, after-mentioned processing at the focus lensposition on the infinity side, and If not, it proceeds to Step 721.

<Processing at Focus Lens Position on Infinite Side>

In Step 719, the camera microcomputer 116 stores the TVAF evaluationvalue as a TVAF evaluation value on a close side, which is based on theoutput of the sensor that is accumulated when the focus lens is locatedon the close side.

An adding is performed for “Mode” (when it is 4 or more, it is returnedto 0) in Step 720, and it proceeds to Step 708.

The processing in Step 708 and below are as described above.

<Processing when Focus Lens Position is Driven to Close Side>

In Step 721, the camera microcomputer 116 calculates the reciprocationamplitude and the center movement amplitude. Although the details arenot described here, in general, with reference to the depth of focus,the amplitude is made smaller when the depth is shallow and is madelarger when the depth is deep. The reciprocation amplitude denotes amovement amount of the focus lens from the infinity side to the closeside in when there is not a movement of the center position of thereciprocation (center movement). The center movement amplitude denotes amovement amount of the center position of the reciprocation. The cameramicrocomputer 116 calculates the reciprocation amplitude and the centermovement amplitude as a value of a movement amount of an image plain.

In Step 722, the camera microcomputer 116 compares the above-mentionedTVAF evaluation value of the infinity side in Mode=0 with theabove-mentioned TVAF evaluation value of the close side in Mode=2. Ifthe close side TVAF evaluation value is larger than the infinity sideTVAF evaluation value, it proceeds to Step 723. If the close side TVAFevaluation value is not larger than the infinity side TVAF evaluationvalue, it proceeds to Step 724.

In Step 723, the driving amplitude is defined using the followingexpression:driving amplitude=reciprocation amplitude+center movement amplitude

In Step 724, the driving amplitude is defined using the followingexpression:driving amplitude=reciprocation amplitude

In Step 725, the camera microcomputer 116 determines that the focus lensis driven in the close direction on the driving amplitude defined inStep 723 or Step 724.

An adding is performed for “Mode” (when it is 4 or more, it is returnedto 0) in Step 726, and it proceeds to Step 708. The processing in Step708 and below are as described above.

FIG. 8 illustrates a progression of the above-mentioned focus lensoperation over time. The horizontal axis represents time, the concaveupward cycle at the top represents a vertical synchronizing signal ofthe image signal, the diamond shape beneath represents an accumulatingtime of the CMOS sensor, the EV_(x) beneath represents a TVAF evaluationvalue that is obtained at the time, and the bottom represents a focuslens position. The drive of the CMOS sensor will be described withreference to FIG. 9. The left of FIG. 9 illustrates an image plane andscanning lines. The right of FIG. 9 illustrates an accumulating time anda transfer time in each scanning line. Since the CMOS sensor is referredto “rolling shutter” and uses a method of releasing the shutter in eachscanning line, the accumulating time and the transfer time are differentbetween the top and the bottom of the screen as illustrated in FIG. 9.This accumulating time is represented by the diamond shape of FIG. 8.

In this embodiment, as illustrated in FIG. 7, the camera microcomputer116 monitors the TVAF evaluation value while the focus lens 105 is movedto the close side or the infinity side, and the camera microcomputer 116controls driving of the focus lens 105 in the in-focus direction. It isrequired to obtain the TVAF evaluation value from the image signalaccumulated in the CMOS sensor while the focus lens 105 is stopped atthe close/infinity side. The drive of the focus lens 105 must be timeddepending on the accumulating time of the CMOS sensor. It is unnecessaryto stop the focus lens at the close/infinity side during the whole ofthe accumulating time of the CMOS sensor, but it is necessary to stopthe focus lens during the accumulating time of the scanning lines in aTVAF frame that is set as a part of an image. The TVAF evaluation valueEV₃ for charge accumulated in the CMOS sensor during the accumulatingtime 3 is imported to the lens microcomputer 115 at the time T₃, and theTVAF evaluation value EV₅ for charge accumulated in the CMOS sensorduring the accumulating time 5 is imported at the time T₅. At the timeT₆, the camera microcomputer 116 compares the TVAF evaluation values EV3and EV5. If EV₅>EV₃ is satisfied, the position of the reciprocationcenter is moved, while if EV₅>EV₃ is not satisfied, the position of thereciprocation center is not moved. As above, the camera microcomputer116 determines the in-focus direction and the in-focus state.

The following is a description of FIG. 10. The horizontal axis denotes atime, and the processing of the camera microcomputer 116 and the lensmicrocomputer 115 during one vertical synchronizing time period areillustrated. First, the camera microcomputer 116 performs a firstfixed-length serial packet communication (first communication)immediately after the vertical synchronizing signal is output, and thecamera microcomputer 116 receives information in the lens unit from thelens microcomputer 115 (for example, data including a focus lensposition or a stop position). The camera microcomputer 116 receives, asdata regarding the AE control, data of the stop position from the lensmicrocomputer 115 in the first communication and therewith transmitscontrol data of the stop and the like. Although it is not illustrated,the lens microcomputer 115 performs a stop drive control within theperiod from after the first communication to the next firstcommunication (within one vertical synchronizing time period) on thebasis of the control data of the stop that is obtained in this firstcommunication. This first communication or after-mentioned secondcommunication is performed by an interactive packet serial communicationas illustrated in FIG. 11. A clock signal is output from the cameramicrocomputer 116 that generates the vertical synchronizing signal ofthe image pickup element. The lens microcomputer 115 executes aprocessing in synchronization with the vertical synchronizing signal bystarting an internal processing in synchronization with an initiatoryclock signal of the first communication that is transmitted from thecamera microcomputer 116. In this embodiment, the first communication isperformed immediately after the vertical synchronizing signal is output,but the invention is not limited to the configuration and it is onlynecessary that the first communication is started in synchronizationwith the output of the vertical synchronizing signal. For example, thefirst communication may be started at the predetermined time periodafter the vertical synchronizing signal is output.

After the first communication, the camera microcomputer 116 acquires theTVAF evaluation value (and the AE evaluation value), performs the TVAFcontrol, and generates the next focus lens driving instruction. Afterthe end of the TVAF control, the camera microcomputer 116 transmits dataincluding the focus lens driving instruction to the lens microcomputer115 in a second fixed-length packet serial communication (secondcommunication). The focus lens driving instruction includes informationon the reciprocation amplitude and the center movement amplitude asinformation on a drive target position of the focus lens. Further, thefocus lens driving instruction includes information on a drive delaytime period that is a timing of starting a drive of the focus lens. Whenthe TVAF is not completed due to error or the like within thepredetermined time period, the camera microcomputer 116 performs thesecond communication when a predetermined time period elapses after thevertical synchronizing signal is output. In this case, the lensmicrocomputer 115 holds data that is previously received. The lensmicrocomputer 115 calculates a focus drive target position after thefocus lens driving instruction is received. At this time, information onthe reciprocation amplitude or the center movement amplitude that istransmitted from the camera microcomputer 116 is a value of a movementamount of the image plane, and therefore the lens microcomputer 115converts the received value to a real focus drive target position inview of the sensitivity for lens. Next, the lens microcomputer 115performs a drive processing of the focus lens when the drive delay timeperiod elapses after the vertical synchronizing signal is output.

The camera microcomputer 116 performs the AE control after the secondcommunication, and generates the next stop driving instruction. Sincethe camera microcomputer 116 performs the AE control after the secondcommunication, a feedback of the AE control delays compared as that ofthe AF control. This is because the responsiveness of the AF control haspriority over that of the AE control. In particular, in order to preventthat the brightness on the screen suddenly changes in a still imageshooting with a state where a live view image is displayed or a movingimage shooting, the camera microcomputer 116 performs a control so as toslowly move the stop 103. In the meantime, it is desirable that the AFcontrol is immediately performed. If the AE control is performed at thesame time as the AF control (these are processed at the same time afterthe first communication), there is a delay in transmitting the focusdriving instruction in the second communication. Therefore, in thisembodiment, in order to make the responsiveness of the AF control apriority, the AF control is performed after the first communication andthe AE control of performing a slow control to prevent the sudden changeof the brightness on the screen is performed after the secondcommunication.

FIG. 12 illustrates contents of the communication between the cameramicrocomputer 116 and the lens microcomputer 115. This illustrates onlydata used in the present embodiment.

The first communication communicates data including:

-   lens microcomputer→camera microcomputer    -   stop position    -   focus lens position-   camera microcomputer→lens microcomputer    -   stop target position    -   stop drive speed        The second communication communicates data including:-   camera microcomputer→lens microcomputer    -   focus target position    -   focus drive speed    -   drive delay time period    -   effective bit of the driving instruction        Furthermore, header data indicating the contents of the        communication and check sum data to confirm whether the        operation of the communication is ensured. In addition, “m” that        denotes the number of commands communicated in the first        communication is larger than “n” that denotes the number of        commands communicated in the second communication.

As to the AE control, the lens microcomputer 115 transmits informationon the stop position to the camera microcomputer 116 in the firstcommunication, and the camera microcomputer 116 performs the AE controlbased on the received information on the stop position after the secondcommunication. Then, the camera microcomputer 116 transmits stop driveinformation including the stop target position and the stop drive speedto the lens microcomputer 115 in the first communication of the nextvertical synchronizing time period.

As to the AF control, the lens microcomputer 115 transmits informationon the focus lens position to the camera microcomputer 116 in the firstcommunication, and the camera microcomputer 116 performs the AF controlbased on the information on the focus lens position after the firstcommunication. When the AF control is completed, the secondcommunication is performed, and the camera microcomputer 116 transmitsfocus lens drive information including the focus target position, thefocus drive speed, and the drive delay time period to the lensmicrocomputer 115.

Even when the AF processing is not completed within the predeterminedtime period after the vertical synchronizing signal is output, thesecond communication is performed after the predetermined time periodelapses. In this case, even if the AF processing is not completed, datafor the fixed-length packet communication is included in an area of thefocus driving instruction of the second communication, and a wrong focusdriving instruction in the AF control is transmitted in the secondcommunication. Accordingly, as illustrated in FIG. 16, when the AFcontrol is not completed within the predetermined time period due to theburden of the camera processing and the like, the wrong focus drivinginstruction is transmitted from the camera microcomputer 116 to the lensmicrocomputer 115. As a result, the lens microcomputer 115 executes awrong focus drive and a malfunction occurs in the side of the lens unit117.

The present embodiment is characterized by using the effective bit ofthe driving instruction, which is a predetermined data area in thesecond communication, in order to prevent the occurrence of themalfunction. The effective bit of the driving instruction will bedescribed with respect to FIG. 17. The camera microcomputer 116 clearsthe effective bit of the driving instruction after the firstcommunication illustrated in FIG. 17 (that is, at a timing of Step 504in FIG. 5). As described above, the invention is not limited to thistiming. When the AF control is completed within a period between thefirst communication and the second communication, the cameramicrocomputer 116 sets the effective bit of the driving instruction atthe time of the completion of the AF control. The setting and theclearing are switched by making the signal level of the effective bit ofthe driving instruction different from each other. This effective bit ofthe driving instruction is not set until the completion of the AFcontrol (until Step 611 in FIG. 6).

In the meantime, the lens microcomputer 115 determines whether theeffective bit of the driving instruction transmitted from the cameramicrocomputer 116 in the second communication is set or cleared. If theeffective bit of the driving instruction is set, the lens microcomputer115 determines the focus lens driving instruction received from thecamera microcomputer 116 in the second communication is valid. If theeffective bit of the driving instruction is cleared, the lensmicrocomputer 115 determines the focus lens driving instruction receivedfrom the camera microcomputer 116 is invalid.

When the AF control is completed within the predetermined time period(the left of FIG. 17), the camera microcomputer 116 sets the effectivebit of the driving instruction. In this case, the lens microcomputer 115acquires the set effective bit of the driving instruction and the focuslens driving instruction in the second communication. The lensmicrocomputer 115 determines that the acquired focus lens drivinginstruction is valid, and can appropriately drive the focus lens inaccordance with the driving instruction of the focus lens. When the AFcontrol is not completed within the predetermined time period (the rightof FIG. 17), the camera microcomputer 116 does not set the effective bitof the driving instruction. In this case, the lens microcomputer 115acquires the cleared effective bit of the driving instruction and thefocus lens driving instruction in the second communication. Then, thelens microcomputer 115 determines that the acquired focus lens drivinginstruction is invalid, and keeps the focus lens driving instructionacquired in the last time second communication in defiance of theinvalid focus lens driving instruction. Accordingly, even if the lensmicrocomputer 115 receives a wrong focus lens driving instruction fromthe camera microcomputer 116 in the second communication, the lensmicrocomputer 115 does not drive the focus lens on the basis of thewrong focus lens driving instruction. Therefore, the malfunction doesnot occur.

As above, in the embodiment, the camera microcomputer 116 transmits, tothe lens microcomputer 115 along with the focus lens drivinginstruction, information on whether the focus lens driving instructionis valid or not. The lens microcomputer 115 can determine whether thefocus lens driving instruction received from the camera microcomputer116 is correct or wrong by receiving the information on whether thefocus lens driving instruction is valid or not. Therefore, even if awrong focus lens driving instruction is transmitted from the cameramicrocomputer 116, the lens microcomputer 115 in this embodiment canprevent a malfunction of executing the drive of the focus lens using thewrong focus lens driving instruction.

In addition, a plurality of types of the effective bit of the drivinginstruction may be set in accordance with the AF control. In thisembodiment, the focus lens drive information is transmitted using thesame communication format between the reciprocating and thepeak-climbing drive. It may be shown whether the transmitted focus lensdrive information is the drive information of the reciprocating, thedrive information of the peak-climbing drive, or the information of thestopping instruction, according to the effective bit of the drivinginstruction.

In order to drive the focus lens 105 on the basis of the verticalsynchronizing signal, the present invention performs the fixed-lengthpacket communication (first communication) immediately after thevertical synchronizing signal is output, and controls the drive of thefocus lens 105 by causing the processing of the lens unit 117 to delayby a certain time period on the basis of the vertical synchronizingsignal. In a system of emphasizing the timing of the communication asabove, it is desirable to cancel the delay in the communication. Thedelay in the communication can be cancelled by preliminarily defining acontent which is communicated at a predetermined timing (secondcommunication) and then preparing the communicated content by thepredetermined timing in the real operation.

On the other hand, in a command communication used when a still image isshot without a live view, it is not determined when and what content istransmitted and received. In this command communication, as illustratedin FIG. 13, the camera microcomputer 116 transmits a command to the lensmicrocomputer 115 to require data of the lens unit or to control theoptical member. After the command is received, the lens microcomputer115 analyzes the command to start the operation, and prepares data thatis returned to the camera. In this case, since the lens microcomputer115 recognizes the instruction from the camera microcomputer only afterthe command is analyzed, delay or the like may be caused. However, thecommand communication has an advantage in a communication that does nothave a periodicity. In other words, it may have an advantage in term ofenabling the command to be transmitted from the camera microcomputer 116to the lens microcomputer 115 at arbitrary time regardless of the cycle.

In the camera system of this embodiment, a command communication methodand a communication method of communicating at a fixed length insynchronization with the vertical synchronizing signal can be switched.

Next, the peak-climbing drive operation will be described with respectto FIG. 14.

Step 1401 indicates a start of the processing.

In Step 1402, the camera microcomputer 116 waits the output of thevertical synchronizing signal to time the communication.

In Step 1403, the camera microcomputer 116 communicates with the lensmicrocomputer 115 and acquires the information on the focus lensposition.

In Step 1404, the camera microcomputer 116 calculates a peak-climbingdrive speed. Although the details are not described here, in general,with reference to the depth of focus, the speed is reduced when thedepth is shallow and increased when the depth is deep. As a result, achange amount of blur becomes more certain to a viewer, and viewingdiscomfort is reduced or disappears.

The camera microcomputer 116 determines whether the TVAF evaluationvalue is smaller by a predetermined amount than the last time TVAFevaluation value in Step 1405. If the TVAF evaluation value is notsmall, it proceeds to Step 1406, and if the TVAF evaluation value issmall, it proceeds to Step 1412. The predetermined amount denotes avalue determined in view of S/N of the TVAF evaluation value, and is notless than a range of fluctuation of the TVAF evaluation value when theobject is fixed and the focus lens position is certain. Otherwise thefluctuation of the TVAF evaluation value has an influence, and thepeak-climbing drive cannot be performed in a correct direction.

In Step 1406, the camera microcomputer 116 determines whether the focuslens 105 reaches an infinity end. The infinity end denotes a positionthat is determined in design choice and is closest to the infinity sidein a stroke of the focus lens. If the focus lens reaches the infinityend, it proceeds to Step 1407. If the focus lens does not reach theinfinity end, it proceeds to Step 1408.

In Step 1408, the camera microcomputer 116 determines whether the focuslens 105 reaches a close end. The close end denotes a position that isdetermined in design choice and is closest to the close side in thestroke of the focus lens. If the focus lens reaches the close end, itproceeds to Step 1409. If the focus lens does not reach the close end,it proceeds to Step 1410.

In each of Step 1407 and 1409, a flag that stores an opposite end isset, and it proceeds to Step 1414 and the peak-climbing drive iscontinued after the focus lens 105 is turned around in the oppositedirection.

In Step 1410, the peak-climbing drive of the focus lens 105 is performedat the speed determined in Step 1404 in the last time forward direction.In Step 1411, the camera microcomputer 116 transmits the communicationdata determined in Step 1410 and Step 1414 to the lens microcomputer115. Then, it returns to Step 1402 and the processing is continued.

In Step 1412, if the peak of the TVAF evaluation value has not beenexceeded and the TVAF evaluation value has decreased, it proceeds toStep 1413. If the peak of the TVAF evaluation value has been exceededand the TVAF evaluation value has decreased, it proceeds to Step 1415and the peak-climbing drive is ended, and it proceeds to Step 1416 andthe processing is ended to transition to the reciprocating operation.

In Step 1413, the camera microcomputer 116 determines whether the TVAFevaluation value decreases a predetermined number of times in a row. Ifthe TVAF evaluation value decreases the predetermined number of times ina row, it proceeds to Step 1414, otherwise it proceeds to Step 1410.

In Step 1410, the peak-climbing drive of the focus lens 105 is performedat the speed determined in Step 1404 in the last time forward direction.In Step 1411, the camera microcomputer 116 transmits the communicationdata determined in Step 1410 to the lens microcomputer 115. Then, itreturns to Step 1402 and the processing is continued.

In Step 1414, the focus lens 105 is peak-climbing driven at a speeddetermined in Step 1404 in a direction opposed to the last timedirection. In Step 1411, the camera microcomputer 116 transmitscommunication data determined in Step 1410 to the lens microcomputer115. Then, it returns to Step 1402 and it processing is continued.

FIG. 15 illustrates a movement of the focus lens 105 in thepeak-climbing drive operation. The “A” (illustrated in solid line)represents an operation of determining that there is an in-focusposition because the peak of the AF evaluation value has been exceededand the AF evaluation value has decreased, of ending the peak-climbingdrive operation, and of transiting the reciprocating operation. Incontrast, the “B” (illustrated in dotted line) represents an operationof determining that the direction is wrong because no peak is found andthe AF evaluation value decreases, and of continuing the peak-climbingdrive operation.

As described above, the camera microcomputer 116 performs a control sothat the TVAF evaluation value is constantly maximum by moving the focuslens 105 while the operations “rebootdetermination→reciprocating→peak-climbing drive→reciprocating→rebootdetermination” are repeated, and the in-focus state is maintained.

The present embodiment separately performs at least two kinds offixed-length packet serial communication (first communication and secondcommunication) during a predetermined cycle (one vertical synchronizingtime period) in an interchangeable lens system. In other words, in thevertical synchronizing time period, which is an output cycle of thevertical synchronizing signal, the first communication and the secondcommunication are separately performed. Moreover, the camera performs anAF control within a time period between the first communication and thesecond communication, and transmits the focus lens driving instructionto the lens unit in the second communication immediately after the AFcontrol. As above, the camera performs the AF control based on thelatest information of the lens position, and can immediately output thefocus lens driving instruction. Therefore, the present invention candecrease the delay of the control cycle and improve a responsiveness ofthe AF.

Further, in the second communication, the camera transmits, to the lensunit along with the focus lens driving instruction, information whetherthe focus lens driving instruction is valid or not. On the basis of theinformation whether the focus lens driving instruction is valid or not,the lens unit can determine whether the focus lens driving instructionreceived from the camera is correct or incorrect. Therefore, even if anincorrect focus lens driving instruction is transmitted from the camera,the lens unit of this embodiment can prevent a malfunction of executingthe drive of the focus lens in accordance with the incorrect focus lensdriving instruction.

An example of a lens unit including a focus lens and a stop as anaccessory has been described in the above embodiment, but the presentinvention is not limited to the configuration. For example, the presentinvention may be a strobe apparatus that includes at least two opticalmembers as other accessories and is capable of being put on and takenoff from the camera.

While the present invention has been described with reference to anexemplary embodiment, it is to be understood that the invention is notlimited to the disclosed exemplary embodiment. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2012-004725, filed on Jan. 13, 2012, and Japanese Patent Application No.2012-127915, filed on Jun. 5, 2012, which are hereby incorporated byreference herein in their entirety.

What is claimed is:
 1. An image pickup apparatus capable of detachablymounting a lens unit including a plurality of optical members thatincludes a stop and a focus lens, the image pickup apparatus comprising:an image pickup unit configured to accumulate charge in synchronizationwith a vertical synchronizing signal to generate an image signal; and acontrol unit configured to generate control information for each of thestop and the focus lens of the mounted lens unit and configured tocommunicate the control information with the lens unit, wherein thecontrol unit is configured to perform first communication insynchronization with the vertical synchronizing signal, and to performsecond communication before the next first communication that isperformed in synchronization with the next vertical synchronizingsignal, wherein each of the first communication and the secondcommunication is packet communication for communicating predeterminedinformation at a fixed-length, and wherein the control unit isconfigured to receive first information including information on thestop and the focus lens from the lens unit in the first communication,generate the control information for each of the stop and the focus lenson the basis of the first information received in the firstcommunication, transmit the control information for the focus lens tothe lens unit in the second communication following the firstcommunication, and then transmit the control information for the stop tothe lens unit in the next first communication.
 2. The image pickupapparatus according to claim 1, wherein the control unit is configuredto control the focus lens before controlling the stop on the basis ofthe first information received in the first communication.
 3. The imagepickup apparatus according to claim 1, wherein, in the secondcommunication, the control unit is configured to transmit, along withthe control information for the focus lens, information indicatingwhether the control information is valid to the lens unit.
 4. The imagepickup apparatus according to claim 1, wherein, in a case thatgeneration of the control information for the focus lens is notcompleted within a predetermined time period after the verticalsynchronizing signal is output, the control unit is configured totransmit, in the second communication, information indicating that thecontrol information is invalid along with the control informationrelating to the focus lens.
 5. The image pickup apparatus according toclaim 1, wherein, in a case that generation of the control informationfor the focus lens is not completed within a predetermined time periodafter the vertical synchronizing signal is output, the control unit isconfigured to set a signal level in a predetermined data area in thesecond communication to a first level, and in a case that the generationof the control information for the focus lens is completed within thepredetermined time period after the vertical synchronizing signal isoutput, the control unit is configured to set the signal level of thepredetermined data area in the second communication to a second levelthat is different from the first level.
 6. The image pickup apparatusaccording to claim 1, wherein after the first communication, the controlunit is configured to generate the control information for the focuslens on the basis of the first information received in the firstcommunication, and then transmit the control information for the focuslens to the lens unit in the second communication following the firstcommunication.
 7. The image pickup apparatus according to claim 1,wherein after the second communication following the firstcommunication, the control unit is configured to generate the controlinformation for the stop on the basis of the first information receivedin the first communication and the image signal, and then transmit thecontrol information for the stop to the lens unit in the next firstcommunication.
 8. The image pickup apparatus according to claim 1,wherein the first communication includes information relating to aposition of the stop and a position of the focus lens.
 9. The imagepickup apparatus according to claim 1, wherein a number of commandscommunicated in the first communication is larger than a number ofcommands communicated in the second communication.
 10. A lens unitcapable of being detachably mounted on an image pickup apparatusincluding an image pickup unit that accumulates charge insynchronization with a vertical synchronizing signal to generate animage signal, the lens unit comprising: a plurality of optical membersincluding a stop and a focus lens; and a lens control unit configured tocommunicate with an image pickup apparatus to which the lens unit ismounted and to control a drive of the stop and the focus lens on thebasis of information received from the image pickup apparatus, whereinthe lens control unit is configured to perform first communication insynchronization with the vertical synchronizing signal received from theimage pickup apparatus, and to perform second communication before thenext first communication that is performed in synchronization with thenext vertical synchronizing signal, wherein each of the firstcommunication and the second communication is packet communication forcommunicating predetermined information at a fixed-length, and whereinthe lens control unit is configured to transmit first informationincluding information on the stop and the focus lens to the image pickupapparatus in the first communication, receive control information forthe focus lens generated on the basis of the first information from theimage pickup apparatus in the second communication following the firstcommunication, and then receive control information for the stopgenerated on the basis of the first information from the image pickupapparatus in the next first communication.
 11. The lens unit accordingto claim 10, wherein the lens control unit is configured to transmit thefirst information including information relating to a position of thestop and a position of the focus lens to the image pickup apparatus inthe first communication.
 12. The lens unit according to claim 10,wherein the lens control unit is configured to control a drive of thefocus lens on the basis of the control information for the focus lensreceived from the image pickup apparatus in the second communication.13. The lens unit according to claim 12, wherein the lens control unitis configured to limit the drive of the focus lens on the basis of thecontrol information for the focus lens received from the image pickupapparatus in the second communication in a case that a signal level of apredetermined data area in the second communication is a first level.14. The lens unit according to claim 12, wherein, in a case that asignal level of a predetermined data area in the second communication isa first level, the lens control unit is configured to control the focuslens on the basis of the control information for the focus lens receivedfrom the image pickup apparatus in the previous second communication.15. The lens unit according to claim 14, wherein in a case that thesignal level of the predetermined data area in the second communicationis a second level that is different from the first level, the lenscontrol unit is configured to control the drive of the focus lens on thebasis of the control information for the focus lens received from theimage pickup apparatus in the second communication.
 16. The lens unitaccording to claim 10, wherein the lens control unit is configured tocontrol a drive of the stop on the basis of the control information forthe stop received from the image pickup apparatus in the firstcommunication.
 17. The lens unit according to claim 10, wherein thefirst communication includes information relating to a position of thestop and a position of the focus lens.
 18. The lens unit according toclaim 10, wherein a number of commands communicated in the firstcommunication is larger than a number of commands communicated in thesecond communication.
 19. A method of controlling an image pickupapparatus capable of detachably mounting a lens unit including aplurality of optical members that includes a stop and a focus lens, saidmethod comprising the steps of: accumulating charge in synchronizationwith a vertical synchronizing signal to generate an image signal;receiving first information including information on the stop and thefocus lens from the lens unit in first communication, wherein the firstcommunication is performed in synchronization with the verticalsynchronizing signal; generating control information for each of theplurality of the stop and the focus lens of the mounted lens unit on thebasis of the first information received in the first communication;transmitting the control information for the focus lens to the lens unitin second communication, wherein the second communication is performedbefore the next first communication that is performed in synchronizationwith the next vertical synchronizing signal; and transmitting thecontrol information for the stop to the lens unit in the next firstcommunication, wherein each of the first communication and the secondcommunication is packet communication for communicating predeterminedinformation at a fixed-length.
 20. A method of controlling a lens unitthat includes a plurality of optical members including a stop and afocus lens, and is capable of being detachably mounted on an imagepickup apparatus including an image pickup unit that accumulates chargein synchronization with a vertical synchronizing signal to generate animage signal, said method comprising the steps of: transmitting firstinformation including information on the stop and the focus lens to theimage pickup apparatus in first communication, wherein the firstcommunication is performed in synchronization with the verticalsynchronizing signal received from the image pickup apparatus; receivingcontrol information for the focus lens generated on the basis of thefirst information from the image pickup apparatus in secondcommunication, wherein the second communication is performed before thenext first communication that is performed in synchronization with thenext vertical synchronizing signal; controlling a drive of the focuslens on the basis of the control information for the focus lens receivedfrom the image pickup apparatus; receiving control information for thestop generated on the basis of the first information from the imagepickup apparatus in the next first communication; and controlling adrive of the stop on the basis of the control information for the stopreceived from the image pickup apparatus, wherein each of the firstcommunication and the second communication is packet communication forcommunicating predetermined information at a fixed-length.
 21. An imagepickup apparatus capable of detachably mounting a lens unit including aplurality of optical members that includes a focus lens, the imagepickup apparatus comprising: an image pickup unit configured toaccumulate charge in synchronization with a vertical synchronizingsignal to generate an image signal; and a control unit configured togenerate control information for each of the plurality of opticalmembers of the mounted lens unit and configured to communicate thecontrol information with the lens unit, wherein the control unit isconfigured to perform first communication in synchronization with thevertical synchronizing signal, and to perform second communicationbefore the next first communication that is performed in synchronizationwith the next vertical synchronizing signal, wherein each of the firstcommunication and the second communication is packet communication forcommunicating predetermined information at a fixed-length, and wherein,in the first communication, the control unit is configured to transmitthe control information for the optical member other than the focus lensto the lens unit, and in the second communication, the control unit isconfigured to transmit, along with the control information for the focuslens, information indicating whether the control information is valid tothe lens unit.
 22. A lens unit capable of being detachably mounted on animage pickup apparatus including an image pickup unit that accumulates acharge in synchronization with a vertical synchronizing signal togenerate an image signal, the lens unit comprising: a plurality ofoptical members including a focus lens; and a lens control unitconfigured to communicate with an image pickup apparatus to which thelens unit is mounted and to control a drive of each of the plurality ofoptical members on the basis of information received from the imagepickup apparatus, wherein the lens control unit is configured to performfirst communication in synchronization with the vertical synchronizingsignal received from the image pickup apparatus, and to perform secondcommunication before the next first communication that is performed insynchronization with the next vertical synchronizing signal, whereineach of the first communication and the second communication is packetcommunication for communicating predetermined information at afixed-length, wherein the lens control unit is configured to control adrive of the focus lens on the basis of information received from theimage pickup apparatus in the second communication, and to control adrive of the optical member other than the focus lens on the basis ofinformation received from the image pickup apparatus in the firstcommunication, and wherein the lens control unit is configured to limitthe drive of the focus lens on the basis of the information receivedfrom the image pickup apparatus in the second communication in a casethat a signal level of a predetermined data area in the secondcommunication is a first level.